Several steps in semiconductor wafer processing require the uniform distribution of a processing solution over the surface of a wafer being processed. In particular, photoresist, developer and scrubbing solutions must be applied to the wafer reiteratively during the process of doping the wafer to produce semiconductor circuits. In order to assure complete and uniform coverage of the wafer surface the solutions are applied to the wafer and the wafer is then spun on a chuck. The centrifugal force of the spinning solution spreads it evenly over the surface of the wafer. Such apparatus is found, for instance, in the commercially available models LSI 45/50/60/ and Kasper System 4500 wafer processing equipment currently available from Eaton Corporation, Microlithography Systems Division, 4001 North First Street, San Jose, Calif. 95134.
Wafer processing equipment typically employs servo motors for spinning the wafer. The motors are deployed in an upright position, the motor vertically oriented, and the motor shaft is coupled to a spindle which accommodates a chuck which is a fixture to secure the wafer. The chuck includes an aperature in fluid communication with the interior of the spindle shaft via which a vacuum force is to be applied to hold a wafer on the chuck. Thus, these motors are typically termed "spindle drive motors."